The present application claims priority of Finnish Patent Application 20010015, filed Jan. 5, 2001.
The present invention relates to an X-ray imaging apparatus for carrying out scanning x-ray imaging, the X-ray imaging apparatus comprising:
an X-ray source in front of the object being imaged for generating X-ray radiation,
a primary collimator for forming an X-ray beam of the X-ray radiation generated and for directing the X-ray beam through the object being imaged, and
X-ray radiation receiving means located behind the object being imaged for receiving X-ray radiation.
The invention is intended for use in X-ray imaging in general, where the radiation receiving means are not in fixed mechanical contact with the radiation source. The invention is applicable, for example, to intraoral imaging, scanning cephalometric imaging, and so-called still imaging. In scanning cephalometric imaging, an X-ray beam located substantially on the vertical plane is directed from the X-ray source through the object being imaged, and the X-ray source is at the same time turned about the rotation centre located between the X-ray source and the line detector camera in order to scan the object being imaged in the horizontal direction, whereby the line detector camera is moved during the scanning movement in such a way that the ray beam meets the vertical slot of the line detector camera. The publication U.S. Pat. No. 5,511,106 discloses this type of scanning cephalometric imaging method. The earlier Finnish patent application FI 20000369 by the applicant of the present application discloses a scanning cephalometric imaging method, in which the effective focal spot of the X-ray source is transferred from the rotation centre to the focal spot of the X-ray source by transferring the rotation centre by means of a transverse linear movement with respect to the ray beam. In still imaging, the imaging is carried out on the whole object to be imaged at once.
When cephalometric imaging is carried out according to the method relating to the application FI 20000369, manufacturing tolerances, for example, may cause the ray beam to move at a different speed or in incorrect alignment with respect to the collimator or detector, in which case there is a risk of the radiation being incorrectly aligned, that is, the ray beam does not meet the active imaging area of the imaging detector, thus necessitating a retake and possibly exposing a patient or personnel unnecessarily to radiation. Furthermore, the movements are only linked with each other programmatically, which means that a possible error in the control electronics may also result in incorrect alignment of the radiation. Correspondingly, also in other methods of X-ray imaging, where there is no fixed mechanical connection between the X-ray source and the radiation receiving means, similar incorrect alignment of radiation may occur.
Accordingly, one important aim of the present invention is to provide an X-ray imaging apparatus, by means of which the above-mentioned disadvantages can be eliminated. To achieve this aim, the X-ray imaging apparatus relating to the invention is characterised in that the X-ray imaging apparatus comprises X-ray radiation identifying means for producing a control signal, on the basis of which control signal the position of the X-ray beam emitted from the X-ray source with respect to the X-ray radiation receiving means can be located and, if necessary, the ray beam can be directed inside the imaging area of the radiation receiving means, and on the basis of which control signal the movements of the apparatus required by scanning imaging can be adjusted so as to be synchronised with each other.
If necessary, the apparatus relating to the invention can also be used to help in directing radiation to the imaging detector, for example, in still imaging.